加工履歷對聚碳酸酯/結晶性塑膠□混物的高階結構暨製品性能的影響之研究

Abstract

高分子□混材料能改善原材料之物理性質，並藉以創造出新的功能。本研究乃利用聚碳酸酯(PC)與結晶性高分子材料，如高結晶性之順排聚丙烯(iPP)或半結晶性之聚醚醚酮(PEEK)進行機械式□混，以創製出有別於單一原材料特性之新穎性材料。研究中設計製作了一個往復式高剪切速率機構，於射出成形的保壓階段進行長時間之高剪切速率操作，以探討在不同的成形加工履歷下，對成形件之高階組織形態暨製品性能之影響。第一部分實驗主要探討相形態與機械性質受到各種不同的加工履歷之影響層面，實驗過程則結合本實驗室發展之試片處理及形態觀察技術，觀察材料高階結構的變化，並與成形件的機械性質量測結果一併討論。實驗結果顯示，在iPP基材中加入約低於20%的少量PC，其試片之抗拉強度會較純iPP為高。此外，經過剪切操作後能有效促進相形態之方向性分佈及大部分比例之抗拉強度。當PC含量低於25%時，剪切型試片之抗拉強度將超過純iPP之一般型試片。iPP含量愈高，經剪切操作後之抗拉強度愈高。本實驗亦探討PC/iPP□混物於工業應用之可行性，當PC含量低於25%，經剪切操作後將具有工業應用之價值。 由於目前尚少有對PC/PEEK□混物之耐熱性、熱穩定性及其相互作用效應進行研究的報告，故第二部分實驗主要探討PC與PEEK□混之可行性，並透過各種特定的蝕刻處理程序，藉由光學顯微鏡觀察，以瞭解PC/PEEK□混物之相形態情形。研究發現，若PC為較小相時，可採用丙酮及二乙基三胺(DETA)進行試片處理。若PEEK為較小相時，可採用50%之鉻酸水溶液進行試片處理。PC與PEEK在20/80之比例下，具有極佳之相溶性，故各種蝕刻方法均無法有效地分辨PC及PEEK相。DSC分析顯示，除了PC/PEEK(20/80)□混物外，其它比例均為部份相溶，因兩成分的Tg的差值隨著PEEK含量的增加而遞減。然而，某些特定比例，如PC/PEEK(20/80)，由於在熔融態僅呈現單一Tg點，故具有可相溶性。此結果亦經由焓鬆弛法、相形態觀察及持溫裂解實驗之PC淨重量損失予以證明

Polymer blends can modify physical characteristics of raw materials, creating a novel performance. In this study, polycarbonate (PC) and crystalline polymer, isotatic polypropylene (iPP) or Poly ether ether ketone (PEEK), are extruded by a mechanical blending extruder to process novel materials with various characteristics in raw materials. A reciprocated mechanism for shearing is also designed to perform long-term shearing at a high shear rate in the packing stage of injection molding and to investigate how processing history affects product performance. The first part of this study focuses mainly on the phase morphologies and mechanical properties affected by the various processing histories. Additionally, experiments involving specimen preparation approaches are performed, along with observations made to examine and discuss the change of phase morphology with the measured results of mechanical property for the molding specimens. Experimental results indicate that adding a slight amount of PC into the iPP matrix, i.e., less than 20%, increases the tensile strength of specimens. Additionally, the phase orientation is improved and most of the tensile strength of the blends increases after shearing. The tensile strength of the shearing specimens with a PC content under 25% exceeds that of the normal specimens of pure iPP. Moreover, a higher iPP content corresponds to a higher tensile strength after shearing. The feasibility of using PC/iPP blends in industrial applications is also investigated, indicating that shearing is valuable in industrial applications when the PC content in PC/iPP blends is under 25%. Whereas heat resistance, thermal stability and the effect of interaction on PC/PEEK blends have received limited attention in literature, the second part of this study attempts not only to determine whether PC should be blended with PEEK, but also to elucidate the phase morphology of the PC/PEEK blends by optical microscopy (OM), following specific etching procedures. According to those results, acetone and DETA can be used to prepare specimens if PC is the minor phase in PC/PEEK blends. Furthermore, 50% CrO3 should be used to prepare specimens if PEEK is the minor phase. PC and PEEK are quite miscible with each other in a 20/80 ratio, explaining why etching methods are ineffective in discriminating between PEEK and PC phases. DSC measurements reveal that the PC/PEEK blends, except for PC/PEEK(20/80), may be partially miscible, as evidenced by the decrease in the differences between the Tg values of PC and PEEK with increasing PEEK content. However, specific compositions, e.g., the PC/PEEK (20/80) blend, are miscible in the melting state and exhibit a single Tg. This finding was also confirmed by the enthalpy relaxation method, phase morphologies and the net PC weight loss determined by holding-temperature degradation.